1. Technical Field of the Invention
The present invention relates to a pneumatically driven liquid supply apparatus adapted in particular for use in a washing step in semiconductor manufacturing process.
2. Description of Prior Art
A washing method widely used during the process of manufacturing semiconductors or the like generally involves immersing objects to be processed, such as semiconductor wafers or glass substrates for LCDs (hereinafter called "wafers"), into a series of washing tanks, each filled with a washing liquid such as a chemical or a rinse liquid (pure water).
A liquid supply apparatus known in the art as a washing apparatus for performing the above washing process is provided with a washing tank filled with a washing liquid such as a chemical or a rinse liquid (pure water), into which the wafer or the like is immersed; a circulatory liquid supply apparatus that allows washing liquid to overflow from the washing tank and also allows it to recirculate and be supplied; and a liquid supply apparatus for replenishment that replenishes the washing liquid, such as a chemical, into the washing tank.
This liquid supply apparatus is also provided with a liquid supply means such as a reciprocating circulatory pump for supplying the washing liquid to the washing tank and a pulsation damping means such as a damper for controlling any pulsations in the liquid on the discharge side of the circulatory pump, in such a manner that the pump and the damper are connected to an air source via an air-pressure adjustment means, such as a regulator, and an electromagnetic switching valve, and that a predetermined air pressure is thereby supplied to the pump and damper, and a predetermined quantity of the washing liquid is circulated and supplied to the washing tank. In addition, a reciprocating type of pump such as a bellows pump is used as a liquid supply means for replenishment, such as a chemical replenishment pump, for supplying into the washing tank a predetermined quantity of a chemical that is within a chemical replenishment tank, this pump is connected to an air source via a regulator and an electromagnetic switching valve, and thus a predetermined quantity of the chemical is supplied into the washing tank by the supply of a predetermined air pressure thereto.
In the above described pneumatically driven liquid supply apparatus using air pressure, there is a danger that liquid within the liquid pipeline could flow backward into the air supply pipeline because of abrasion due to long-term usage or some other cause. If this backflow of liquid within the air supply pipeline occurs, the liquid will intrude into the components of the air-pressure adjustment means, that is, the electromagnetic switching valve and regulator thereof, and damage this electromagnetic switching valve and regulator, make them unable to function, and disable the supply of liquid.
The present invention was made in the light of the above described problem and has as an object thereof the provision of a pneumatically driven liquid supply apparatus that is configured in such a manner to detect any backward flow of the liquid within the air supply pipeline through the pump and damper, and prevent damage or halting of the functions of the air-pressure adjustment means due to such backflow.